The purpose of prison is to punish and to protect society — not to rehabilitate.

For the past quarter-century or so, this has been the stated policy of Florida.

Florida was a leader among the states in rejecting the liberal philosophy of the 1960s and 1970s that crime was foremost a "social problem" that needed sociological solutions.

You know what? It worked.

Without question, a guy sitting in prison is not free to break into your house or mine. He is not free to stick up a convenience store, or to deal drugs on the street corner.

So as Florida rapidly expanded its prison system starting in the 1980s, the crime rate fell steadily. There were other reasons, but having so many people behind bars certainly helped.

But there is a cost, too.

As of Friday, there were 99,845 inmates in the Florida system, the nation's third-largest, housed in 60 prisons, 41 work or forestry camps, and assorted work-release centers and road prisons.

The Department of Corrections has an annual budget of $2.3-billion. The average cost of keeping an inmate for one year is more than $19,000.

On top of that, the department's secretary, Walter McNeil, predicts the state will need to build another 19 prisons over the next five years at a capital cost of another $2-billion, even if we stack 'em and rack 'em. Incidentally, this is close to the size of the state's current budget deficit.

A lot of the department's customers are repeat offenders. About 33 percent of inmates come back to prison within three years of their release. Of the current inmate population, 46 percent have been there before.

But when inmates successfully complete a substance abuse program, their three-year rate of recidivism is only 6.7 percent, according to the department.

Furthermore, for each additional year of education they achieve, their chance of coming back to prison drops 3 to 4 percentage points.

And so there has been a subtle and interesting trend in the rhetoric of the Department of Corrections under Gov. Charlie Crist, who once advocated prison chain-gangs.

No one is resurrecting the old R-word, "rehabilitation." But a new R-word is coming into use: "re-entry."

"Re-entry is a cost-saving measure," says department spokeswoman Gretl Plessinger, who says 88 percent of inmates eventually get out.

"It's also an anti-crime measure, because if they have the tools to succeed, they are less likely to victimize again."

Plessinger estimates that two-thirds of all admitted inmates have a substance-abuse problem, but the department's resources allow only about 20 percent to go through a program.

Wrestling with the state budget, the Legislature has cut the department's programs. Next spring the department will ask for some of those cuts to be restored.

No one is talking here about crime being "society's fault." No one is wringing hands and boo-hooing over the fact criminals are in prison. No one is talking about being soft.

The question instead is whether it becomes cheaper in the long run to attack recidivism, so that fewer crimes are committed, than to wait until they are committed and warehouse the offenders.

There is a reason why the air in Tampa Bay is filled with playoff talk. If Thursday night's 12-8 Bucs preseason win over the Jaguars is any indication, it's also going to be filled with footballs thrown by quarterback Jameis Winston.